Minor drop in central heating pressure.

Kashkai

Ok, so I tempted fate by thinking my water leak was solved, but today I noticed that the water pressure had dropped from 0.9 bar, where its been for 2 months now to 0.8 bar. The wife had the heating on for a few hours last Friday when the pressure climbed to 1.3 bar and then gradually started dropping back when the system was cooling. However, its now dropped below 0.9 bar for the first time since I thought it had been fixed.

Is this because the damn leak is still there or is it because dissolved air has been pushed out of the water (the system was refilled from 0 bar when it was repaired). If so, how can I raise the pressure back up? I have a fill valve on the pipework in the hotpress but when I turn it, nothing happens.

Buford T Justice

If the system was drained down and refilled it could be the air in the water coming out of it over time. Did you check the rads to see if there was any air in them?

Plombier

I think your expansion vessel is burst or may need to be recharged.When your heating is on the water expands has nowhere to go so the pressure increases.

reilig

Prosperous Dave wrote: »

Ok, so I tempted fate by thinking my water leak was solved, but today I noticed that the water pressure had dropped from 0.9 bar, where its been for 2 months now to 0.8 bar. The wife had the heating on for a few hours last Friday when the pressure climbed to 1.3 bar and then gradually started dropping back when the system was cooling. However, its now dropped below 0.9 bar for the first time since I thought it had been fixed.

Is this because the damn leak is still there or is it because dissolved air has been pushed out of the water (the system was refilled from 0 bar when it was repaired). If so, how can I raise the pressure back up? I have a fill valve on the pipework in the hotpress but when I turn it, nothing happens.

It is most likely air and can take a few months to get it out of the system.

Your fill valve is propably set to fill your system to somewhere between 0.8 bar and 1 bar. That is why nothing happens when you turn it on. It may need to be below 0.75 bar before it will start to fill the system. Give it a chance, run the system for a while and it should settle down.

reilig

Plombier wrote: »

I think your expansion vessel is burst or may need to be recharged.When your heating is on the water expands has nowhere to go so the pressure increases.

I doubt it. The pressure will increase in the system until it reaches the pressure in the expansion vessel. After this, the system's pressure will not increase - instead the diaphragm inside the expansion vessel will move out of shape to maintain the pressure in the system - IYKWIM

Bruthal

reilig wrote: »

I doubt it. The pressure will increase in the system until it reaches the pressure in the expansion vessel. After this, the system's pressure will not increase - instead the diaphragm inside the expansion vessel will move out of shape to maintain the pressure in the system - IYKWIM

Well id say as the pressure vessel bladder begins to get compressed the pressure in the system does then go up, i mean if the bladder is reduced 50 percent in volume by the expanding water then the pressure must be double in the bladder and therefor on the water side of the diaphram also i would of thought.

Bruthal

Prosperous Dave wrote: »

Ok, so I tempted fate by thinking my water leak was solved, but today I noticed that the water pressure had dropped from 0.9 bar, where its been for 2 months now to 0.8 bar. The wife had the heating on for a few hours last Friday when the pressure climbed to 1.3 bar and then gradually started dropping back when the system was cooling. However, its now dropped below 0.9 bar for the first time since I thought it had been fixed.

Is this because the damn leak is still there or is it because dissolved air has been pushed out of the water (the system was refilled from 0 bar when it was repaired). If so, how can I raise the pressure back up? I have a fill valve on the pipework in the hotpress but when I turn it, nothing happens.

I would`t be all that concerned about that slight drop, If disolved air came out of the water the pressure would go up, Possibly some air within a rad or the system has come out the automatic air bleed unit. Or the temperature within the whole system when off has dropped slightly because its a bit cooler now weather wise.

Kashkai

The reason I'm worried about it is that I want to put down a new wooden floor but would be more than a little peeved if the leak reappeared to ruin the new floor like the old one.

ntpm

Pressure fluctuation from 0.8bar when cold to 1.3bar when hot is within normal range.

If you are worried that there is still a leak make sure the filling loop/ makeup valve is fully shut. If you do have a leak the pressure will drop to zero eventually.
Some plumbers tend to adjust the automatic filling loop pressure to say 1.0bar and leave the valve open. This then automatically "tops up" the system if pressure reduces. I do not recommend this as it could cover up any leaks and keep introducing fresh water into the system which will cause corrosion. ( However, If this is happening you would see problems like exessive air in raditors).

If you have a gas boiler the boiler will normaly not come on if pressure drops below a given pressure eg. 0.5 bar (safety controls).

But if you have an oil boiler it will try and run but you should notice that rads or water in cylinder is not getting hot and the boiler may trip out on high limit stat.

Kashkai

The thing is that the auto fill valve doesn't apear to be working. When the plumber fixed my system, he tried to refill the pipework by using the auto fill valve beside the cylinder but nothing happened. Then he had to refill the system by connecting a hose up to the outside oil boiler and pouring water in that way.

I have the auto fill valve turned off for the very reason that you stated, i.e. if there is still a leak then the autofill valve (if it is still working, although I don't believe so) will disguise the leak by topping up the system. My concern is that the pressure held stable for 2 months (admittedley while the heating wasn't turned on) but after using the heating for a couple of hours one day, the pressure fell, albeit only a little, from 0.9 bar to 0.8 bar. There isn't any air in the radiators btw

I was going to redecorate the hallway and put down a new wooden floor next weekend but I'm not so sure now as I don't want to have to rip it all back up again if this damn leak returns.

Finally, any idea why the autofill valve has stopped working? The pressure guage was down to zero a few months back btw.

ntpm

Prosperous Dave wrote: »

The thing is that the auto fill valve doesn't apear to be working. When the plumber fixed my system, he tried to refill the pipework by using the auto fill valve beside the cylinder but nothing happened. Then he had to refill the system by connecting a hose up to the outside oil boiler and pouring water in that way.

I have the auto fill valve turned off for the very reason that you stated, i.e. if there is still a leak then the autofill valve (if it is still working, although I don't believe so) will disguise the leak by topping up the system. My concern is that the pressure held stable for 2 months (admittedley while the heating wasn't turned on) but after using the heating for a couple of hours one day, the pressure fell, albeit only a little, from 0.9 bar to 0.8 bar. There isn't any air in the radiators btw

I was going to redecorate the hallway and put down a new wooden floor next weekend but I'm not so sure now as I don't want to have to rip it all back up again if this damn leak returns.

Finally, any idea why the autofill valve has stopped working? The pressure guage was down to zero a few months back btw.

As earlier threads stated the reduction may be because some of the air in the system got moved round and may have vented through the automatic air vents.
Also as the ambient temperatures are droping the pipes in the floor/ building are getting a bit colder and this may evident in the lower pressure reading of 0.8Bar.
I would normally leave the standing pressure when cold at 1.0 bar.
I think that your system seems ok. However, let it run for a few weeks and monitor the pressure. If there is a leak it may be more apparent when the system heats up.

Get the Reducer valve replaced anyway. You may need to slighly top up the system at some point and you want to ensure that any components are working correctly.

reilig

My concern is that the pressure held stable for 2 months (admittedley while the heating wasn't turned on)

Now that you are using your heating, the water is being heated and this adds a small bit of air to the system initially. Once the water in the system has been heated a few times, the air will go out through the air valves and your system will maintain its pressure.

Kashkai

Any idea why the auto fill valve has stopped working? The tap will turn on and off to its full extent but no water will get into the system. Is it an airlock, stuck valve etc etc???

Kashkai

I now have a daily ritual of checking the pressure guage in my hotpress when the system is cold and when hot.

Today, the guage is reading 0.5bar when cold, the lowest its been to date. This has steadily fallen from 0.9 bar a month ago since we turned the heating back on. I was going to relay the wooden floor this week but now I think I still have a leak somewhere.

I was in B & Q yesterday and they have Fernox leak sealant that can be connected to a rad's bleed valve and squirted in using a caulk gun. Should I try this or just continue to monitor the guage to see if it goes any lower?

BTW, the autofill valve is not working as I can't re-pressurise the system.

reilig

The air should be gone out of it by now. What you need to keep an eye on now is that the pressure doesn't go under .5 bar when the boiler gets cold. If it does, then you may have a leak. The leak sealer might be worth a go.

Bruthal

There has been a drastic drop in ambient temp as well which will reduce the cold pressure somewhat as the water gets cooler when the heating is off.

I think the manual fill setup is better maybe.